The Dynamic Cone Penetrometer

“The DCP”

Gavin P. Gautreau, P.E.

Geotechnical Research Manager

Louisiana Transportation Research Center (LTRC)

• Purpose & Concept

• Parts

• Operation/Technique

• Data Recording

• Calculations/Analysis

• Advantages/Disadvantages

• Implementation

Presentation Objectives:

• Purpose & Concept

– Dynamic Cone Penetrometer

– Shallow Pavement Applications

– Measures Stiffness, mm/blow

– Simple Concept

• Stiff material requires more drops

• Weak material requires fewer drops

– Non Nuclear

– Design Information

– Quick and Cost Effective

– Another “Tool for the Toolbox”

• Parts– Handle

– Upper Rod (5/8” dia)

– Hammer

• 17.8 pounds (8kg)

• 22.6 inch drop

– Anvil & Lower Rod

– Cone Tip (60 degree, ¾” dia)

– Measuring Stick with cm & mm divs.

– Other

• Hammer Drill

• Generator

• Farm Jack

• Operation (Preparation)

– Hammer Drill

• Quickly thru Asphalt or

Concrete

• Minimal Intrusion

• Various Length bits

• Dry vs wet coring rig

– Crew

• Operator

• Reader

• Recorder

(A)(B)

• Operation cont’d

– Record reference reading (A)

• Measuring stick is stationary

– Lift hammer to handle

– Release hammer

– Record reading after hammer

drop (B)

– Repeat drop, read and record

each drop thru pavement

layers(?)

(A)(B)

• Technique

– Keep straight (vertical)

– Avoid banging hammer

into handle during lift.• Can lose disposable cone

• Damage to device

– Spin rod after each drop.

– Keep ruler stationary

– Record reading after

every hammer drop.

(X)

(Y)

• Data Recording (Currently developing TR method)

– Project Information

• Site Location

• Station #

• Distance from Centerline

• Elevation (if available)

– Pavement Information (as available)

• Cross-Section Thickness Information

• Material Types (classification and gradation)

• Compaction Info (Proctor Moisture and Density) as

available

• Nuclear Gauge Information if available

(A) 46.0(B) 46.3

2 46.6

3 46.9

4 47.2

5 47.5

? ???

Top of Asphalt/Concrete

Top of Testing Surface

(bottom of drilled hole, if applicable)

Reading after First Blow

Reading after Second Blow

Anytown, LA – Hwy 1, Sta. 19+00 RL

Blow

#

Rod

Reading

0 NA

0 46.0(A)

Reading after Fourth Blow

Reading after Third Blow

Reading after Last Blow

Reading after Fifth Blow

• Data Recording, example

1 46.3(B)

,cm

example: stone base

Field Data

• Data Calculations (without drilling)

Blow

#

Rod

Reading, cm

0 NA

0 46.0

1 46.3

2 46.6

3 46.9

4 47.2

5 47.5

6 47.8

Distance

per Blow

Cumulative

Penetration

Distance below Surface

cm

this times

ten = DCPI

cm

Running Total

cm

can plot as inches or elev.

0.0 0.0equal to tip location

below surface

0.3 0.3 0.3

0.3 0.6 0.6

0.3 0.9 0.9

0.3 1.2 1.2

0.3 1.5 1.5

0.3 1.8 1.8

Field Data

• Data Calculations (drilling occurred)

Blow

#

Rod

Reading, cm

0 38.4

0 46.0

1 46.3

2 46.6

3 46.9

4 47.2

5 47.5

6 47.8

Distance

per Blow

Cumulative

Penetration

Distance below Surface

cm cm

Running Total

cm

can plot as inches or elev.

7.6Drilled depth

0.0tip location

below pavement surface

0.3 0.3 7.9

0.3 0.6 8.2

0.3 0.9 8.5

0.3 1.2 8.8

0.3 1.5 9.1

0.3 1.8 9.4

• Data Analysis

– Plotting Data

– Layer Changes

– Avg. mm/blow

Example, cont’d

0

5

10

15

20

25

30

35

40

0 20 40 60 80

Number of Blows

Cum

ula

tive P

enetr

ation,

cm

Anytown, LA – Hwy 1, Sta. 19+00 RL

3 mm/blowLayer Change

Layer Change

36 mm/blow

11.2 mm/blow

Number of Blows

De

pth

of P

en

etr

atio

n, cm

150+50 Rt Ln

2 mm/blow

4 mm/blow

6 mm/blow

8 mm/blow

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200Number of Blows

Cu

mu

lative

pe

ne

tra

tio

n,c

m

161+50 Lt Ln

2 mm/blow

4 mm/blow

6 mm/blow

8 mm/blow

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200

Number of Blow s

Cum

ula

tive p

enetr

atio

n,c

m

190+00 Lt Ln

2 mm/blow

4 mm/blow

6 mm/blow

8 mm/blow

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200

Number of Blow s

Cum

ula

tive p

enetr

atio

n,c

m

176+00 Lt Ln

2 mm/blow

4 mm/blow

6 mm/blow

8 mm/blow

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200Number of Blows

Cu

mu

lative

pe

ne

tra

tio

n,c

m

Recent Analysis

Example

1.310.9

56.3

0.72.2

20.3

0.62.9

18.3

1.85.5

37.2

Resilient Modulus Equations

• DCP - Direct Model

• DCP-Soil Property Model

d

rDCPI

M 42.01

0.221

32.1

DCPIM r

14.122

For Cohesive Soils: 1<Mr<14 ksi

Equations from LTRC Project 03-3P

R2 = 0.82

R2 = 0.89

DCPI

DCP Tests

ALF Lane 4

Base, Treated Subase, & Subgrade

Field & Laboratory Test Summary

Cross-Section

• Asphalt Surface (2”)

• Base (8.5”)– Stone

– BCS with 10% Slag

– BCS with FlyAsh (small untreated area at end)

– Foamed Asphalt

• Treated Subbase (12”)– Lime

– Cement

• Untreated Subgrade Co

ns

tru

cti

on

SUBGRADE DCP VALUES

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

20-Nov 10-Dec 30-Dec 19-Jan 8-Feb

TIME, DATE

AV

ER

AG

E M

M /

BL

OW

1A AVERAGE

2A AVERAGE

2A 0+10

1B AVERAGE

2B AVERAGE

3A AVERAGE

3B AVERAGE

November

Average =

28.9

February

Average =

13.6

TREATED SUBBASE DCP VALUES

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

20-Nov 10-Dec 30-Dec 19-Jan 8-Feb

TIME, DATE

AV

ER

AG

E M

M /

BL

OW

1A AVERAGE

2A AVERAGE

2A 0+10

1B AVERAGE

2B AVERAGE

3A AVERAGE

3B AVERAGE

Lime

Initial

Average

= 31.8

Cement

Average

= 5.3

Cement

Initial

Average

= 20.3

Lime

Average

= 7.3

BASE DCP VALUES

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20-Nov 10-Dec 30-Dec 19-Jan 8-Feb

TIME, DATE

AV

ER

AG

E M

M /

BL

OW

1A AVERAGE

2A AVERAGE

2A 0+10

1B AVERAGE

2B AVERAGE

3A AVERAGE

3B AVERAGE

BASE DCP VALUES

BCS & Slag

BCS & Fly Ash

BCS (Raw)

Stone

Stone

Foamed Asphalt

Foamed Asphalt

Each point represents 3 tests

per section per date.

DCP Advantages:

• Determines Stiffness in mm/blow

• Layer Changes identified by Slope

Changes

• Minimal surface disturbance

• Not “Rocket Science” and not “Nuclear”

• Method of acceptance and verification

• Design and Strength information via

Correlations (CBR, Mr, etc.)

• Simple reliable, cost-effective tool for

shallow pavement applications

Depth

Blow Count0Layer

Layer

Layer

• Disadvantages:

• Not for use on large stone, shell, asphalt, or

concrete

• DCP can break under repetitive drops in

very stiff material or with improper removal

• Does not measure moisture content or

density (only measures stiffness)

• Develop a comprehensive implementation plan for

the DCP with procedures that DOTD can use in its

daily production

• Develop or modify current DOTD specifications to

accommodate such changes.

LTRC Project: 06-4GT

Objectives:

This is a comprehensive follow-up study after four

LTRC research projects on involving DCP

applications.

Implementation

• Develop a device that can collect soil moistures

and soil penetration resistance.

LTRC Transportation Innovation Research

Exploration (TIRE) Project: 07-2TIRE

Objective:

Combined Soil Moisture Meter and Dynamic Cone

Penetrometer (DCP)

Professor Martin Feldman, LSU

Implementation

Questions?

Thanks,

Drive Safely